'\" te
.\"  Copyright 1989 AT&T
.\"  Copyright (c) 2006, Sun Microsystems, Inc.,  All Rights Reserved
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
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.TH PULLUPMSG 9F "Jan 16, 2006"
.SH NAME
pullupmsg \- concatenate bytes in a message
.SH SYNOPSIS
.LP
.nf
#include <sys/stream.h>



\fBint\fR \fBpullupmsg\fR(\fBmblk_t *\fR\fImp\fR, \fBssize_t\fR \fIlen\fR);
.fi

.SH INTERFACE LEVEL
.sp
.LP
Architecture independent level 1 (DDI/DKI).
.SH PARAMETERS
.sp
.ne 2
.na
\fB\fImp\fR\fR
.ad
.RS 7n
Pointer to the message whose blocks are to be concatenated. \fBmblk_t\fR is an
instance of the \fBmsgb\fR(9S) structure.
.RE

.sp
.ne 2
.na
\fB\fIlen\fR\fR
.ad
.RS 7n
Number of bytes to concatenate.
.RE

.SH DESCRIPTION
.sp
.LP
The \fBpullupmsg()\fR function tries to combine multiple data blocks into a
single block. \fBpullupmsg()\fR concatenates and aligns the first \fIlen\fR
data bytes of the message pointed to by \fImp\fR. If \fIlen\fR equals \fB-1\fR,
all data are concatenated. If \fIlen\fR bytes of the same message type cannot
be found, \fBpullupmsg()\fR fails and returns \fB0\fR.
.SH RETURN VALUES
.sp
.LP
On success, \fB1\fR is returned; on failure, \fB0\fR is returned.
.SH CONTEXT
.sp
.LP
The \fBpullupmsg()\fR function can be called from user, interrupt, or kernel
context.
.SH EXAMPLES
.LP
\fBExample 1 \fRUsing \fBpullupmsg()\fR
.sp
.LP
This is a driver write \fBsrv\fR(9E) (service) routine for a device that does
not support scatter/gather \fBDMA\fR. For all  \fBM_DATA\fR messages, the data
will be transferred to the device with \fBDMA\fR. First, try to pull up the
message into one message block with the \fBpullupmsg()\fR function (line 12).
If successful, the transfer can be accomplished in one \fBDMA \fRjob.
Otherwise, it must be done one message block at a time (lines 19-22). After the
data has been transferred to the device, free the message and continue
processing messages on the queue.

.sp
.in +2
.nf

 1 xxxwsrv(q)
 2    queue_t *q;
 3 {
 4	    mblk_t *mp;
 5	    mblk_t *tmp;
 6	    caddr_t dma_addr;
 7     ssize_t dma_len;
 8
 9	    while ((mp = getq(q)) != NULL) {
10	            switch (mp->b_datap->db_type) {
11             case M_DATA:
12	                   if (pullupmsg(mp, -1)) {
13                            dma_addr = vtop(mp->b_rptr);
14	                           dma_len = mp->b_wptr - mp->b_rptr;
15	                           xxx_do_dma(dma_addr, dma_len);
16	                           freemsg(mp);
17	                           break;
18	                   }
19	                   for (tmp = mp; tmp; tmp = tmp->b_cont) {
20                            dma_addr = vtop(tmp->b_rptr);
21                            dma_len = tmp->b_wptr - tmp->b_rptr;
22                            xxx_do_dma(dma_addr, dma_len);
23                    }
24	                   freemsg(mp);
25	                   break;
	            ...
26		        }
27	    }
28 }
.fi
.in -2

.SH SEE ALSO
.sp
.LP
.BR srv (9E),
.BR allocb (9F),
.BR msgpullup (9F),
.BR msgb (9S)
.sp
.LP
\fIWriting Device Drivers\fR
.sp
.LP
\fISTREAMS Programming Guide\fR
.SH NOTES
.sp
.LP
The \fBpullupmsg()\fR function is not included in the \fBDKI\fR and will be
removed from the system in a future release. Device driver writers are strongly
encouraged to use \fBmsgpullup\fR(9F) instead of \fBpullupmsg()\fR.
